International Guild of Knot Tyers Forum

General => Practical Knots => Topic started by: xarax on June 18, 2011, 07:58:58 PM

Title: Penberthy knot
Post by: xarax on June 18, 2011, 07:58:58 PM
   At (1), there is a drawing of the so-called "Penberthy knot", a certain modification of the Prusik knot. (See the attached picture)  I have compared it to a modified ABoK#1740 hitch, ( the ABoK#1740 (b), shown in (2)), and I have found that is not holding as well, tied around a pole or a main line of similar rope diameter. This "Penberthy knot" is, essentially, a type of a simple bowline turned into a hitch, so it can not be tightened easily or  effectively. I  have found that we can pull the nipping loop end (the "b" end) and tighten the hitch, only with much difficulty.The other free end, the collar end (the "a" end ), we can pull it with even greater difficulty, almost not at all  - as it happens in the case of the bowline.
   Am I missing something here ? Does anybody has a personal experience with the Penberthy knot ? What else is known about it ?
  
1) http://72.51.46.77/~alpinejo/Contents/Contents_1970_files/AJ%201970%20272-278%20Equipment.pdf#search=%22knots%22
2) http://igkt.net/sm/index.php?topic=3016.0
Title: Re: Penberthy knot
Post by: Dan_Lehman on June 19, 2011, 04:12:06 PM
Quote
At (2), there is a drawing of the so-called "Penberthy knot",

No there isn't : it's a thread w/images of your modification of an
Ashley knot also presented.

The Penberthy hitch is a curious one in that its behavior differs
depending on the closing of the coil --in contrast to having the
coil closed as a continuous sling into which one will attach the
load with a 'biner, which will adjust position.

--dl*
====
Title: Re: Penberthy knot
Post by: xarax on June 19, 2011, 05:23:28 PM
   Now it is !  :) By a typo, I have written (2) instead of (1). I have since edited the mistake.
   So, now you can click at (1), and see the image that I have copied from there.
   This article seems to me well written. It cites the origin of this picture at the magazine Mountain. (page 272)
    Are you saying that this knot is not THE Penberthy knot/hitch, or that it is only one variation/dressing of it ?
    Anyway, I have not understood why this knot is better than the Prusik, of which it is supposed to be an improvement. I have found it inferior of the improvement of the Ashley#1740, seen at (2).
Title: Re: Penberthy knot
Post by: Transminator on June 20, 2011, 08:41:11 AM
   Anyway, I have not understood why this knot is better than the Prusik, of which it is supposed to be an improvement. I have found it inferior of the improvement of the Ashley#1740, seen at (2).

As far as I can see, it does not say "improvement" in the article but "alternative"

Quote:
> "The new Penberthy ascender knot [140]-a less tiring alternative to the
Prusik knot-eliminates kinking of the rope thus allowing the user to move
it more easily after loading."


One major difference would be that this not does not require a closed loop like the prusik.
This difference could be called an advantage. Another possible advantage is mentioned in
the above quote > eliminates kinking of the rope thus allowing the user to move
it more easily after loading

But these advantages are void because it does not perform well. Either I am
missing something or this knot does not perform at all, actually, at least not as intended.
The bowline-esque structure prevents the knot to clinch down on the rope as the prusik does e.g.
Also it is a lot more complicated to tie then the prusik.
Interesting: when you slide the knot of the rope, you have an eskimo bowline.
Title: Re: Penberthy knot
Post by: xarax on June 20, 2011, 12:18:17 PM
... it does not perform well. Either I am missing something or this knot does not perform at all, actually, at least not as intended.
   The bowline-esque structure prevents the knot to clinch down on the rope as the prusik does e.g.
 
   That is exactly what I, too, have found...However, I do not know if there is a particular dressing that would make a difference...
Title: Re: Penberthy knot
Post by: alpineer on June 20, 2011, 10:36:40 PM
http://storrick.cnc.net/VerticalDevicesPage/Ascender/KnotPages/KnotPenberthy.html (http://storrick.cnc.net/VerticalDevicesPage/Ascender/KnotPages/KnotPenberthy.html)

This knot was designed as a rappelling safety backup to be used below the friction device (i.e. on the brake hand side of the rope) where much less clamping force is needed to be effective. Although I haven't used this knot myself, my understanding is that it can perform well in this configuration. I use the French Prusik(a.k.a Autoblock). 
Title: Re: Penberthy knot
Post by: xarax on June 20, 2011, 11:12:26 PM
   Thank you alpineer,
   Is this the same knot ? A variation of the "helical" knot ? (1) I do not see much of a "helicity" in the "Penberthy knot/hitch" I was talking about... :) The Valdotain climbing knot looks, to me, quite different.

1) http://storrick.cnc.net/VerticalDevicesPage/Misc/RappelSafetyPost.html
Title: Re: Penberthy knot
Post by: alpineer on June 21, 2011, 12:10:39 AM
  Thank you alpineer,
   Is this the same knot ? A variation of the "helical" knot ? (1) I do not see much of a "helicity" in the "Penberthy knot/hitch" I was talking about... :) The Valdotain climbing knot looks, to me, quite different.

1) http://storrick.cnc.net/VerticalDevicesPage/Misc/RappelSafetyPost.html

Your posted diagram shows a single strand wound around a larger diameter rope. That looks like "helicity" to me. As for Storrick's Valdotain, you may be referring to the tressed(braided) version.  
Title: Re: Penberthy knot
Post by: xarax on June 21, 2011, 01:38:47 AM
... a single strand wound around a larger diameter rope. That looks like "helicity" to me.

    :) If that was helicity, all the climbing hitches would be "helical knots" !  :)
    However, I see a relation between the "helical knot" and the "Penberthy knot/hitch" shown above. The later is based upon ( the mechanism of ) a simple/common bowline, while the former is based upon an Eskimo bowline. (See attached picture) The way they are loaded, we should expect that the mechanism of the Eskimo bowline can be tightened easier than the mechanism of the simple bowline. So the "helical" knot would probably hold better than the "Penberthy".

     
Title: Re: Penberthy knot
Post by: Dan_Lehman on June 21, 2011, 07:49:55 AM
Taking Storrick as correct --a safer bet than most you'll ever make,
especially if his opinion is backed by Thrun's--, the knot in the OP
is a variation on the helical (essentially being an eye knot whose
eye is coiled for gripping), and the other distinction is, per Storrick:

Quote
The knot is the Penberthy
 if you tie the ends of the sling together and clip the loop,

 and the Penberthy-Pierson or Vald?tain
 when you clip loops tied in the the free ends.

One advantage of the --per above distinction-- Penberthy is that
it can be quicker/surer to grap and lock.  I have used it in a
sort of self-belay role.  (But I think I've also found that with
a firm cord that the coil can just sliiiiiiAYYYYEEEdde.)
Choose your material(s) carefully!  YMMV!
So, this is a different capability than grip-&-slide : it's
PLEASE-grip-NOW-&-I-won't-bother-you-again action;
the knot will need loosening and re-forming for some
subsequent use, as it extends on taking hold.

--dl*
====
Title: Re: Penberthy knot
Post by: Bob Thrun on June 21, 2011, 08:38:56 AM
This hitch was published by Clarence Cook in anarticle entitled "New Climbing Knot" in the January 1961 D. C. Speleograph.  He did not give the knot a name.  I am enclosing the drawing from that article.  It was redrawn and published with minor changes in the June 1961 NSS News.  Bill Plummer had "Comments" on the same page of the NSS News.  He said "I have tested the helical climbing knot and made the following observations:"  He then gave it an unfavorable review.  I use the name helical knot that Plummer gave it.  Dwight Deal also called it a helical knot in the May 1967 NSS News.  I see that I can drop the resolution of the scan of the June 1961 NSS News page and stay within the attachment limits; I'll try.

Larry Penberthy re-invented this hitch and published it in 1968 in Sheet B-2 of a series of information sheets put out by Mountain Safety Research, a company he formed.  He called it the Penberthy ascender knot or just the Penberthy knot.  He claimed it was an improvement over the "Prusik ascender knot".  The drawings in the Alpine Journal originated in Penberthy's information sheet.  Dick Mitchell gave a talk at an NSS Convention and wrote an article in 1969 where he called it the ascender knot, a name that has been used by some cavers.  Bill Mixon pointed out that the name ascender knot could be confused with mechanical ascenders.

Cavers use the helical knot because it is easier to loosen than a Prusik.  They use as few as three coils of the sling around the main rope.  Penberthy recommended 5 or 6 turns.  Arborists use more coils than cavers.  More coils means it grips better and there can be more slack in the knot, but also means there is more elongation when it is loaded.  It takes some fiddling to get the amount of slack right.  Too loose and the knot slips; too tight and the knot is harder to push up the rope.  Someone who uses helical knots soons learns the right amount of slack.

Chet Hedden's article (1959 and 1960 in different publications) was entitled "A New Climbing Knot".  He did not give the knot any name in his article, but it is always called a Hedden knot.  Cook did not get his name attached to the knot he described, probably because he gave equal credit to Tony Marchi.

The class of hitches that are used for climbing a rope are most widely called "friction hitches".  This is not entirely satisfactory because all knots and hitches have some friction.  The obvious term "climbing knot" is not satisfactory either because, to some people, a climbing knot is any knot that might be used by a climber.  Peter Owen has The Book of Climbing Knots, Michael Noonan has Climbing Knots for Righties and Lefties, and Craig Luebben uses that term in the 2nd edition of his Knots for Climbers.
Title: Re: Penberthy knot
Post by: xarax on June 21, 2011, 10:06:13 AM
   Thank you Bob Thrun,
   A very informatve reply, as always.

  He claimed it was an improvement over the "Prusik ascender knot".
   Cavers use the helical knot because it is easier to loosen than a Prusik.

   So, it was proposed as an improvement, and not just as an alternative.
   It is easier to loosen, indeed, BUT - in the "Penberthy" knot/friction hitch variation ( with the Eskino bowline lock mechanism), more than in the "helical" knot/friction hitch variation ( with the simple/common bowline lock mechanism ) - it is much more difficult to grip ! It really needs some entreaties to get started...

  PLEASE-grip-NOW...

 :)
Title: Re: Penberthy knot
Post by: Transminator on June 21, 2011, 11:53:36 AM
On the second attachment it says: "The prusik knot will always hold better if it is right side up as shown below"
That is bullshoot. < Now modified This is the same as saying: The Prusik with the loop sticking out on the right hand side performs better then the Prusik with the loop on the left hand side. It doesn't. Its the same knot!
> The prusik is symetrical. It works both ways equally well, as there is no difference.

Regarding Penberthy knot and Prusik (or other friction hitches as the Klemheist):
The Penberthy knots seems to be nothing more then a bowline (or eskimo bowline in the other variation) with the loop wrapped several times around the rope before finished. Basically using the bowline as a hitch with several round turns. One can do the same with any fixed loop.

The Prusik or Klemheist perform well because they don't solely rely on the wraps around the rope but more crucially have a mechanism that clamps on those wraps when the end/loop is loaded. The Penberthy does not do that at all. It solely relies on the wraps to bear the load, if they don't (which they won't), the bowline does not serve as a backup at all. So how can that be an improvement? Furthermore: the Prusik does not jam one bit. As soon as the load is off, it can be moved along the rope as easy as pie.
Title: Re: Penberthy knot
Post by: Dan_Lehman on June 21, 2011, 06:33:18 PM
On the second attachment it says: "The prusik knot will always hold better if it is right side up as shown below"
That is [BS] . This is the same as saying: The Prusik with the loop sticking out on the right hand side performs better then the Prusik with the loop on the left hand side. It doesn't. Its the same knot!
> The prusik is symetrical. It works both ways equally well, as there is no difference.

Such language is unwanted here (except by intimation/abbreviation),
and is especially unfortunate when it is so clearly wrong.  You might
take care in faulting something expressly stated (i.e., that suggests
that the particular point was considered, not incidentally involved).

Now, how ... different?!  -- in how the coils are oriented with regard
to the lay of the rope!
  Yes, that is a 1961 presentation, and the
ropes du jour were laid nylon Plymouth Goldline and various other manila
(ideally, much less elastic!) ropes.  In the given image, the "better"
orientation of the Prusik hitch shows the upper, *coil-away*
half of the knot wrapping against the lay, the lower ... with.
Interestingly, the Prusik shown is a "4-coil" (2x2); today, I think
that the 5-coil version is more commonly used, and especially the
coil-away half benefits from more wraps, as it will extend to grip.

Quote
The Penberthy [hitch] seems to be nothing more than a bowline (or eskimo bowline in the other variation)
 with the loop wrapped several times around the rope before finished.
Basically using the bowline as a hitch with several round turns.
One can do the same with any fixed loop.

But one cannot so easily adjust the coils and then tie the eyeknot
if using an eyeknot (e.g., fig.8 ) that needs to have some *pre-knot*
tied awaiting the tail's completion.

Quote
Furthermore: the Prusik does not jam one bit.
As soon as the load is off, it can be moved along the rope as easy as pie.

Pie in the sky  opining here; history (and much usage with
the knot in various circumstances) speaks strongly otherwise.

Do you really think that cavers and arborists --users who depend (or
have done so, before mechanical devices (Jumars)) on hitches to
move up (and down) ropes-- cannot assess these knots, and could
be so wrong about one of the oldest-in-use of them?!

--dl*
====
Title: Re: Penberthy knot
Post by: Dan_Lehman on June 21, 2011, 06:40:43 PM
This hitch ...

Bob, this begs the question, Which hitch?
We've presented several, pointing to the difference between
whether the parts leading away from the coil are tied off
to close a loop that is clipped into or to each
make an attachment to some anchor point, or with them
joined in an eyeknot which delivers the load.  In the first
case, one can expect some bit of tension equalizing around
the clipping 'biner (having taken care to have the end-2-end
knot out of the way); in the latter cases, there is more need
for tyer adjustment of leg tensions, and more risk that the
usage will develop imbalances (perhaps).

--dl*
====

ps:  SS369/Scott, please edit your oversized QUOTE.
(Hey, yeah, I asked for it --quote function use--, but had
in mind proper use!  You need a '[/quote]' inserted before
your reply (which I had until now overlooked, not thinking
that there was one (and, yes, wondering at why ...)).)

 ::)

Title: Re: Penberthy knot
Post by: SS369 on June 21, 2011, 07:39:31 PM
On the second attachment it says: "The prusik knot will always hold better if it is right side up as shown below"
That is bullshoot. This is the same as saying: The Prusik with the loop sticking out on the right hand side performs better then the Prusik with the loop on the left hand side. It doesn't. Its the same knot!
> The prusik is symetrical. It works both ways equally well, as there is no difference.



I notice the date of publicly announcing the holding orientation of the prusik in that publication and it reminds me that knot experimentation and use were with laid ropes and cord. So I think the statement is factual and should be considered strongly if you were to use this knot on laid rope.
With modern ropes the prusik works equally well in both orientations, in my experience.

These slip and grip knots are so very dependent on materials used and I strongly advise personal testing before using in life endangering endeavors.

I went climbing last weekend and had a novice climber with me. We "tested/learned" several grip and slide setups. Some with the rope and cord on hand did well for me and the same did Not as well for him. The only difference was about 30 lbs.

I asked the young man to pick his favorite(s) out of the batch and he picked the "standard" 4 coil prusik and the Blake/Prohaska (4 coil as well) Both of those performed easily and he remembered easily. And that is what counts.
These were only used that day for rope ascension, not for autoblock backup.

Get familiar with them all and see what works for you personally for the given circumstances.

SS

P.S. Sorry Dan, my mega-quote was not to satisfy your earlier request. Crazy cyber demons at work is all.
Title: Re: Penberthy knot
Post by: Bob Thrun on June 22, 2011, 04:34:40 AM
Bill Plummer was the only caver who emphasized tying the Prusik knot right side up.  I have climbed on laid ropes a long time ago.  On some of the climbs I had one knot oriented so I could loosen and move it with my left hand.  I never noticed any difference in holding power because I never encountered a marginal situation.  It would be a very narrow band of conditions where there would be a difference.
Title: Re: Penberthy knot
Post by: Transminator on June 22, 2011, 08:12:35 AM
Such language is unwanted here (except by intimation/abbreviation),
and is especially unfortunate when it is so clearly wrong.  You might
take care in faulting something expressly stated (i.e., that suggests
that the particular point was considered, not incidentally involved).

Now, how ... different?!  -- in how the coils are oriented with regard
to the lay of the rope!
 

Point taken and I stand corrected.
I was also hasty in writing it as only later I considered that the author was perhaps referring to the lay
of the rope. I was focused on the knot itself.
I am not editing my post though, otherwise the replies don't make sense anymore.
Title: Re: Penberthy knot
Post by: xarax on August 26, 2013, 06:14:04 PM
  A picture of Penberthy knot, with a short text, in French.